Tire traction device securing apparatus

ABSTRACT

A tire traction device securing apparatus having a plurality of elastic tensioning arms extending radially from a central hub, each of the plurality of elastic tensioning arms removably attachable to a tire traction device to provide a tension force directed toward the central hub to secure the tire traction device to the tire. In an embodiment, the plurality of arms and central hub are of an elastomeric material to form a monolithic body; coupled to each tensioning arm of the monolithic body is a hook to removably attach the tire traction device securing apparatus to the tire traction device and thereby secure the tire traction device to the tire.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuing application of application Ser. No. 11/696,607,filed Apr. 4, 2007, entitled TIRE TRACTION DEVICE SECURING APPARATUS,the disclosure of which is incorporated herein by reference in itsentirety for all purposes.

BACKGROUND OF THE INVENTION

1. Field if the Invention

The present invention relates to tire traction enhancement devices for avehicle wheel assembly. More particularly, the present invention relatesto devices and methods to secure tire traction enhancement devices to avehicle wheel assembly.

2. Discussion of Related Art

Tire traction enhancement devices, referred herein as tire tractiondevices, including those commonly known as tire chains, provideincreased traction to a vehicle wheel assembly. When a tire of a wheelassembly provides inadequate traction for a vehicle, a tire tractiondevice may be installed onto the tire by the operator of the vehicle andemployed until road conditions improve to the point where the tiretraction device becomes unnecessary. Thus, it is important that the tiretraction device be simple to install and remove.

Many tire traction devices, when positioned flat on the ground, areladder-like, having two parallel side chains connected by a plurality oftransverse traction chains. The length of the side chains is generallyapproximately equal to the circumference of the tire, or slightly less,while the length of the traction chains is generally slightly greaterthan the tire tread width. While various tire traction devices mayemploy cables or plastic straps in place of chains, the assembly of suchtire traction devices is similar to those employing chains.

To install a typical tire traction device, it is first draped over thetop of the tire. The length of the traction chains is such that the sidechains form a circle concentric with and adjacent to the sidewall of thetire. A tire traction device securing apparatus, such as that depictedin FIG. 1, is then attached to the side chains to remove the slack fromthe side and traction chains to secure the tire traction device to thetire. Conventional tire traction device securing apparatus 100 includesan elastic loop 110 and a plurality of hooks 120. The plurality of hooks120 may be movable about the elastic loop 110 or may be crimped toelastic loop 120. To install tire traction device securing apparatus100, each hook 120 is attached to a location on a side chain of a tiretraction device. Generally, a first hook is attached, and then a secondhook is selected and attached at another location on the side chain,typically a location approximately 180° from the first attached hook.With two hooks 120 attached, elastic loop 110 is stretched and distortedinto a tight ellipse. After the first two hooks are installed, it isdifficult to install the third hook because one must insert a hand intothis tight ellipse and further stretch elastic loop 110. As hooks areattached, elastic loop 110 must stretch further and so it becomes harderto attach each successive hook 120 to the side chain. Also, afterattaching the first two hooks, the thickness of the loop materialbecomes narrowed from the tension, and the unattached hooks becomemovable about the elastic loop 110 (even if initially crimped to theloop material) and must then be accurately positioned to locations onthe side chain to adequately remove slack from each tire quadrant.However, because the unattached hooks cannot be moved beyond the firsttwo attached hooks, properly securing the tire traction device to thetire requires correctly selecting first two hooks of the plurality andcorrectly positioning them on the side chain. For these reasons it isdifficult to install traction device securing apparatus 100, especiallyduring inclement weather.

Furthermore, because the single elastic loop 110 provides the onlysource of tension, conventional tire traction device securing apparatus100 will fail to secure the tire traction device to the tire if theelastic loop 110 breaks. Hence, because a single break in loop 110 willremove all tension from each of the plurality of hooks 120, completefailure of tire traction device securing apparatus 100 may occur at anytime with little or no warning.

3. Summary of the Invention

Described herein is a tire traction device securing apparatus having aplurality of elastic tensioning arms extending from a central hub; eachof the plurality of elastic tensioning arms may be removably attached toa tire traction device to provide a plurality of independent tensionsources directed toward the central hub of the securing apparatus tosecure the tire traction device to the tire. The plurality of elastictensioning arms provides a plurality of independent tensioning means,easing installation and providing redundancy capable of preventingcatastrophic failure. In an embodiment, the elastic tensioning arms havea greater elasticity than the central hub. In another embodiment, theelastic tensioning arms extend radially from the central hub and eacharm has a length greater than the radius of the central hub. In anembodiment, each of the plurality of elastic tensioning arms has thesame length and across the plurality the angle between adjacent elastictensioning arms is equal, providing an approximately uniform tensionabout a circumference concentric with the central hub and slightlylarger than the circumference defined by the ends of the relaxedtensioning arms opposite the central hub. In an embodiment, the arms andcentral hub form a monolithic body. In a particular embodiment, themonolithic body includes six elastic tensioning arms having a 60° anglebetween adjacent arms; each elastic tensioning arm having a breakingstrength of at least 244 N. In one such embodiment, the monolithic bodyis of an elastomeric material, such as one comprising at least 40%natural rubber. In a further embodiment, proximate to an end of each armopposite the central hub, a hook provides a means to removably attach atensioning arm to the tire traction device such that the elastictensioning arms are approximately radial to the circumference of theside chain of the tire traction device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a conventional tire traction device securing apparatus.

FIG. 2A depicts a vehicle with a tire traction device secured to a tireby a tire traction device securing apparatus in accordance with anembodiment of the present invention.

FIG. 2B depicts an expanded view of a tire traction device secured to atire by a tire traction device securing apparatus in accordance with anembodiment of the present invention.

FIG. 2C is a plan view of a tire traction device securing apparatus inaccordance with an embodiment of the present invention.

FIG. 3 is a perspective view of a central hub of a tire traction devicesecuring apparatus in accordance with an embodiment of the presentinvention.

FIG. 4 is a plan view of an attachment means of a tire traction devicesecuring apparatus in accordance with an embodiment of the presentinvention.

FIG. 5 is a side view of the attachment means depicted in FIG. 4.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In various embodiments, tire traction device securing apparatuses aredescribed with reference to figures. However, certain embodiments may bepracticed without one or more of these specific details, or incombination with other known methods and materials. In the followingdescription, numerous specific details are set forth, such as specificmaterials and dimensions, etc., in order to provide a thoroughunderstanding of the present invention. In other instances, well-knownaspects and features have not been described in particular detail toavoid unnecessarily obscuring the present invention. Referencethroughout this specification to “an embodiment” means that a particularfeature, structure, material, or characteristic described in connectionwith the embodiment is included in at least one embodiment of theinvention. Thus, the appearances of the phrase “in an embodiment” invarious places throughout this specification are not necessarilyreferring to the same embodiment of the invention. Furthermore, theparticular features, structures, materials, or characteristics may becombined in any suitable manner in one or more embodiments.

FIG. 2A depicts a vehicle 200 having a tire traction device 205 securedto tire 220 by a tire traction device securing apparatus 250 inaccordance with an embodiment of the present invention. FIG. 2B depictsan expanded view of the wheel assembly of interest in FIG. 2A. As shownover tire 220 is tire traction device 205 including a traction chain 210and a side chain 215. FIG. 2B further shows tire traction devicesecuring apparatus 250 including a central hub 260, a plurality ofelastic tensioning arms 270 and an attachment means 280. As shown,attachment means 280 removably attaches each elastic tensioning arm 270to side chain 215 to provide a force directed toward central hub 260.Elastic tensioning arm 270 provides tension to tire traction device 205proportional to the elastic deformation the arm is subjected to whentire traction device securing apparatus 250 is removably attached totire traction device 205 on a wheel assembly (as shown in FIG. 2A-2B).When removably attached, the force of elastic tensioning arm 270 removesslack from side chain 215 and traction chain 210 to secure tire tractiondevice 205 to tire 220.

FIG. 2C depicts a plan view of tire traction device securing apparatus250 in accordance with an embodiment of the present invention when it isplaced flat on the ground. Generally, a plurality of elastic tensioningarms and central hub form a substantially planar hub and spoke unit. Ahub and spoke unit enables easy installation and/or removal of tiretraction device securing apparatus 250 because, the plurality oftensioning arms have a fixed radial position. During installation, thefixed radial position dictates where on a tire traction device each armis to be attached. When installed, a hub and spoke unit provides foruniform tension about the circumference of a tire traction device andeliminate slack from each quadrant of the tire to secure the tiretraction device to a tire (as shown in FIG. 2A-2B). In the embodimentshown in FIG. 2C, the plurality of elastic tensioning arms 270 extendoutward from central hub 260 to form a monolithic hub and spoke body. Inan alternate embodiment, the plurality of elastic tensioning arms andcentral hub are separate components forming a hub and spoke assemblythat can be also be manipulated as a unit during installation/removal ofthe tire traction device securing apparatus.

The plurality of elastic tensioning arms includes at least three elastictensioning arms 270 to provide independent sources of tension directedtoward central hub 260 about the circumference of a tire traction deviceon a tire. The plurality of elastic tensioning arms provides redundancycapable of preventing catastrophic failure because a failure in a singletensioning arm does not affect the ability of the remaining tensioningarms to secure the tire traction device. For instance, as few as two ofthe three tensioning arms may be required to secure the tire tractiondevice to a tire and additional redundancy is provided in embodimentsemploying more than three tensioning arms. The at least three elastictensioning arms also more uniformly distribute removal of slack in atire traction device than a single, double-ended, elastic tensioning arm(e.g. a bungee cord). By more uniformly distributing the amount of slacktaken up by each tensioning arm, relatively less slack must beaccommodated by each arm. Therefore, each arm must provide tension overrelatively less radial distance and so must be deformed relatively lessduring installation, thereby enabling easier installation. In anembodiment, there is an even number of elastic tensioning arms. In thespecific embodiment depicted in FIG. 2C, the plurality includes sixelastic tensioning arms 270. The majority of tire traction devices havebetween 12 and 18 side chain segments, a segment being a section of sidechain between two transverse traction chains. Therefore, to provide onetensioning arm for each two or three segments, six arms are necessary.Having no more than six elastic tensioning arms also advantageouslyreduces the amount of labor required in attaching/removing the pluralityof arms. Furthermore, embodiments with six tensioning arms providesignificant tensioning arm redundancy to prevent a catastrophic failureif any tensioning arm happens to break.

The plurality of elastic tensioning arms 270 extend from central hub 260radially. A radial configuration, as shown in FIG. 2C, transmits thetension in each elastic tensioning arm in a direction most closelyapproximating normal to the central hub. Radial configurations arebeneficial where the joint between elastic tensioning arms 270 canwithstand higher tensile stress than shear stress. Radial configurationsare also beneficial in transmitting tension across the diameter of atire traction device. This is particularly true when a first and secondelastic tensioning arm 270 are on opposite sides of central hub 260 andeach arm extends from the central hub in opposite directions, asdiscussed further below.

Generally, the plurality of elastic tensioning arms 270 may have anyangular arrangement about central hub 260 to provide tension, wheninstalled, about the circumference of a tire traction device on a tire.In a particular embodiment, the plurality of elastic tensioning arms 270is symmetrically arranged about central hub 260. In one such embodiment,complete symmetry about the central hub is provided with an even numberof tensioning arms extending radially from the central hub with aconstant azimuth angle, θ, between adjacent tensioning arms. As anexample of this embodiment, FIG. 2C has six elastic tensioning armshaving an azimuth angle of 60° between adjacent tensioning arms. Whentire traction device securing apparatus 250 is installed on a wheelassembly to secure a tire traction device (as shown in FIGS. 2A-2B), asymmetrical arrangement of tensioning arms balances the static tensionin a first tensioning arm with the static tension in a second tensioningarm on an opposite side of the central hub and extending in a directionopposite the first tensioning arm (i.e. tension is balanced between twoarms 280° apart). A balanced tension improves the uniformity of tensionabout the circumference of the tire traction device to better secure thetire traction device to a tire. A balanced tension also enables easyinstallation because little or no torque is imparted on central hub 260during the attachment of elastic tensioning arms 270 to the tiretraction device. Furthermore, each tensioning arm 270 provides only aportion of the total elastic deformation possible by the entireplurality of the tensioning arms. Therefore, the length across any pairof opposing tensioning arms is sufficiently small that when only oneopposing pair is stretched to span the diameter of a tire tractiondevice there is adequate tension to hold the tire traction devicesecuring apparatus on the tire traction device while any remaining armsare attached to the tire traction device. For example, an installationmay proceed by first positioning the radius of the tire traction devicesecuring apparatus 250 parallel to the radius of the vehicle tire andadjacent to the outboard side of the tire. Next, opposing pairs ofelastic tensioning arms may be successively attached to a tire tractiondevice on the tire. Here, a first tensioning arm is attached to a tiretraction device and then a second tensioning arm, extending from thecentral hub in a direction opposite the first, is attached to the tiretraction device to impart an opposing tension in the first and secondtensioning arms. This opposing tension supports the tire traction devicesecuring apparatus while imparting no net torque as the remaining pairsof arms are attached. Removal of tire traction device securing apparatus250 may similarly be facilitated by successively removing opposing pairsof elastic tensioning arms.

The length of each of the plurality of elastic tensioning arms 270 whenrelaxed, as measured from the outer diameter of central hub 260 to theattachment means is herein defined as L_(A). In reference to FIG. 2C,the arm length, L_(A), is measured from the outer diameter of centralhub 260 to the point where elastic tensioning arm 270 couples toattachment means 280. In an embodiment, L_(A) is equal across theplurality of elastic tensioning arms 270 to provide a uniformlydistributed force. However, length, L_(A), may vary to accommodatevarious tire sizes and/or tire traction device circumferences.Generally, the larger the tire, the greater the tire traction devicecircumference and the larger L_(A) must be. For a given tire tractiondevice circumference, the outer diameter of central hub 260 may bevaried as well as L_(A). However, in embodiments where the elasticity ofthe arms is substantially greater than the elasticity of the central hub(discussed further below), L_(A) must be large enough that the arm canbe stretched sufficiently to be attached to the tire traction device. Inone embodiment, L_(A) is less than the radius, R, of central hub 260. Inanother embodiment, L_(A) is greater than the radius, R, of central hub260. In a further embodiment, each of the plurality of elastictensioning arms 270 has an equal length L_(A), wherein L_(A) is at least10% of the radius of the tire upon which tire traction device securingapparatus is to secure a tire traction device. In a particularembodiment, central hub 260 has a radius, R, of 30 mm and L_(A) isapproximately 138 mm to secure a tire traction device to a 225 mm to 800mm radius tire.

Generally, each elastic tensioning arm 270 may have any cross-sectionalshape, such as, but not limited to, square, triangular, rectangular,oval, or circular. Elastic tensioning arm 270 may have anycross-sectional area with a width, W_(A), which is in plane of the planview provided in FIG. 2C, and a thickness that is out of plane of theplan view provided in FIG. 2C. The optimal cross-sectional area of theelastic tensioning arm is dependent on the elastic modulus of theparticular material chosen and the desired securing tension. Bothcross-sectional shape and area may vary across the plurality of elastictensioning arm. A substantially round cross-section provides increasedresistance to cuts and cracks. In a particular embodiment, each elastictensioning arm 270 of the plurality has a substantially roundcross-section having both a width, W_(A), and a thickness ofapproximately 10 mm.

In an embodiment, the plurality of elastic tensioning arms 270 has agreater elasticity (smaller elastic modulus) than central hub 260. Thus,tire traction device securing apparatus 250 includes a plurality ofindependent, distinct regions of relatively higher elasticity(tensioning arms 270) coupled to region of relatively lower elasticity(central hub 260). Because each elastic tensioning arm 270 is distinct,there is little “pre-tensioning” of the tensioning arms duringinstallation, thereby easing the installation of tire traction devicesecuring apparatus 250. With substantially more elastic deformationoccurring in elastic tensioning arms 270 than in central hub 260,unattached tensioning arms may remain relaxed (i.e. do not becomepre-tensioned by the tension in those arms already attached) until eachunattached arm is individually deformed when attached to the tiretraction device.

Generally, each of the plurality of elastic tensioning arms is of amaterial having sufficiently large elastic modulus for the plurality toprovide adequate tension to secure a tire traction device to a tire. Thematerial preferably also has a sufficiently high breaking strength,remains sufficiently elastic across a temperature range of at least −10C to 50 C, and is resistant to the salts and oils commonly known toexist in the typical vehicular environment. In one embodiment, thebreaking strength of each elastic tensioning arm 270 is greater than 244N (i.e. 50 lb-force tensile strength). In another embodiment, elastictensioning arm 270 is comprised of an elastomeric material, such as butnot limited to, natural rubber, silicone rubber, ethylene propylenediene rubber, polyisoprene, polybutadiene, and polyurethane. Thus, inembodiments where the plurality of elastic tensioning arms 270 andcentral hub 260 form a monolithic body, both the central hub andplurality of tensioning arms are comprised of an elastomeric material.In particular embodiments having monolithic elastomeric bodies, asmaller cross-sectional area of elastic tensioning arm through whichtension is applied relative to that of the central hub results in eachtensioning arm having smaller modulus of elasticity than that of thecentral hub (i.e. arms deform to a greater extent than hub). In theparticular embodiment employing an elastic tensioning arm 270 having asquare cross-section of approximately 10 mm on a side, the monolithicelastomeric body is comprised of at least 40% natural rubber. In analternate embodiment wherein elastic tensioning arm 270 and central hub260 form an assembly, elastic tensioning arm 270 may be comprised of acoil spring or elastomeric material, while hub central 260 may becomprised of any commonly known rigid material.

The central hub of the tire traction device securing apparatus may havevarious shapes and dimensions. In one embodiment, central hub 360 hascircular shape about central axis A with a radius, R, sufficiently largethat adjacent elastic tensioning arms 370 are separated from one anotherby a distance S. Such separation isolates tension in one arm fromadjacent arms, some benefits of which were previously discussed, andalso reduces the amount of shear stress at the joint between adjacentarms that could cause a tear between adjacent arms. In embodimentsproviding a separation between adjacent tensioning arms, the minimumouter diameter of central hub 360 depends on the number of elastictensioning arms 270 and the width, WA, of each arm. In an embodiment,the maximum radius, R, of central hub 360 is limited to half the radiusof the circle defined by the end of the elastic tensioning arms 270opposite the central hub, when the arms are relaxed. Limiting themaximum radius of the central hub advantageously keeps the hub away fromthe objects which may damage it, such as curbs. This is particularlyimportant for embodiments where the central hub is shaped like a torus(discussed further below) because damage could then lead to loss oftension in multiple tensioning arms. In one embodiment employing sixtensioning arms, each having a width, WA, of approximately 10 mm, theradius, R, of central hub 360 is approximately 30 mm.

Central hub 360 may be a solid disc or, as shown in FIG. 3, central hub360 may include at least one perforation 362. Perforation 362 mayprovide elasticity to the central hub and/or provide a means restrainingthe plurality of tensioning arms 370 when a tire traction devicesecuring apparatus is not securing a tire traction device to a tire(e.g. during storage of the tire traction device securing apparatus). Inan embodiment, perforation 362 is sufficiently large relative to theouter radius, R, that central hub 360 has the shape of a torus, whereinthe cross-sectional area 363 of the torus is approximately the same asthe cross-sectional area 373 of elastic tensioning arm 370. In one suchembodiment, the torus-shaped central hub has elasticity comparable tothe elasticity of elastic tensioning arm 370. In the embodiment depictedin FIG. 3, a single perforation 362 forms central hub 360 into a torushaving an inner diameter (I.D.) sufficiently large to contain at leastthree elastic tensioning arms when either inserted through perforation362 or hooked to the torus-shaped central hub 360. In an alternateembodiment, the central hub includes a plurality of perforations, eachperforation having a diameter sufficient to removably attach attachmentmeans 280 (as shown in FIG. 2C) to the central hub when a tire tractiondevice securing apparatus is not securing a tire traction device to atire.

In an alternate embodiment, perforation 362 merely serves as anaesthetic feature of central hub 360. Similarly, to further increaseaesthetic appeal, various aspects of the present invention may bemodified. For example, a twist may also be provided along thelongitudinal axis of each elastic tensioning arm 370 (not shown).Central hub 360 may also be given a pleasing appearance, such as a torus(i.e. donut) shape, a star shape, a solid disc shape, or a sphericalshape. Aesthetics may further be enhanced by coloring the elastictensioning arms and central hub. In one such embodiment, both elastictensioning arms 270 and central hub 260 are a vivid orange.

Referring back to FIG. 2C, proximate to an end of each elastictensioning arm 270 opposite central hub 260 is attachment means 280.Attachment means 280 serves to removably attach tire traction devicesecuring apparatus 250 to a tire traction device on a tire (as shown inFIG. 2A-2B). Attachment means 280 may simply comprise a perforation inelastic tensioning arm 270 to which any commonly known fastener on atire traction device may be coupled. Alternatively, attachment means 280further comprises a distinct material coupled to elastic tensioning arm270, the distinct material capable of commonly known fastening modes,such as, but not limited to, hooking, snapping, or screwing, to a tiretraction device. In a particular embodiment, shown in plan view in FIG.4, attachment means 480 comprises a fastener having first end 490passing through perforation 482 in elastic tensioning arm 470. As shown,elastic tensioning arm 470 may be locally enlarged to accommodateperforation 482 and prevent tear outs when under tension. Fastener firstend 490 is crimped over end tab 485, thereby securing first end 490 toelastic tensioning arm 470. Fastener second end 495 is hooked to providean attachment point for a tire traction device. In an embodiment,attachment means 280 comprises a fastener of a material different thanthat of elastic tensioning arm 470, such as metal or rigid plastic. FIG.5 further depicts a side view of attachment means 480 showing fastenerfirst end 490 crimped about the end of elastic tensioning arm 470 andfastener second end 495 hooked with a gap, G, of approximately 10 mm toprovide an point for attaching the tire traction device securingapparatus to a tire traction device.

Although the present invention has been described in language specificto structural features and/or methodological acts, it is to beunderstood that the invention defined in the appended claims is notnecessarily limited to the specific features or acts described. Forexample, many applications may benefit from the tire traction devicesecuring apparatus in accordance with the present invention and one ofordinary skill in the art would recognize the embodiments described asparticularly graceful implementations of the claimed invention usefulfor illustrating the present invention.

1. A tire traction device securing apparatus comprising: at least threeelastic tensioning arms coupled to a central hub, the tensioning armsextending radially from the central hub at a fixed radial position aboutthe central hub; and a fastener at an end of each of the at least threeelastic tensioning arms opposite the central hub, the fastenersconfigured to removably attach to a tire traction device to provide aradial tension force to secure the tire traction device to a tire. 2.The apparatus of claim 1, wherein each of the at least three elastictensioning arms, when untensioned, remain at the fixed radial positionabout the central hub, and have a length, measured from an outerdiameter of the central hub to the fastener, that is greater than theouter diameter of the central hub.
 3. The apparatus of claim 1, whereinthe at least three elastic tensioning arms are of an elastomericmaterial containing at least one component selected from the groupconsisting of: natural rubber, silicone rubber, ethylene propylene dienerubber, polyisoprene, polybutadiene, and polyurethane.
 4. The apparatusof claim 3, wherein the elastomeric material comprises at least 40%natural rubber.
 5. The apparatus of claim 1, wherein each of the atleast three elastic tensioning arms has a breaking strength of at least244 N.
 6. The apparatus of claim 1, wherein each of the at least threeelastic tensioning arms and the central hub are comprised of anelastomeric material to form a monolithic hub and spoke unit.
 7. Theapparatus of claim 1, wherein the at least three elastic tensioning armsare of equal lengths, widths and thickness and positioned in the fixedradial position with a same angle between adjacent elastic tensioningarms to provide an approximately equal tension force between the centralhub and at least three positions of a side chain on the tire tractiondevice.
 8. The apparatus of claim 7, comprising six elastic tensioningarms having a 60° angle between adjacent elastic tensioning arms.
 9. Theapparatus of claim 1, wherein the fastener comprises: a first endpassing through an eye proximate to the end of the tensioning armopposite the central hub, the first end of the fastener crimped aboutthe end of the tensioning arm; and a second end of the fastener having ahook to removably attach to the tire traction device.
 10. The apparatusof claim 9, wherein the hook forms a gap between a second end of thehook and itself of at least 10 mm to removably attach to a side chain ofthe tire traction device.
 11. The apparatus of claim 1, wherein thecentral hub is torus-shaped having a cross-sectional area greater than across-sectional area of one of the elastic tensioning arms.
 12. Theapparatus of claim 1, wherein each of the at least three elastictensioning arms has a length of at least 135 mm measured from an outerdiameter of the central hub to a point where the tensioning arm couplesto the means to removably attach the tensioning arm to the tire tractiondevice.